Rules ignoring input item

Hi sorry for my bad english.
Simple program for door sensor with mqtt broker and notification with openhab cloud.

Item file

// Items file
//Security items
Switch SecuritySystem "SecuritySystem"
Contact DoorSensor "Door Sensor [%s]" <door> {mqtt="<[broker:Home/Security/Sensor1:state:default]"}

Mqtt it workin i view change open/closed.

Rules file

//rules file
rule "Door sensor"
    item DoorSensor received update OPEN
    if(SecuritySystem.state == ON)
      SendBroadcastNotification("Door is opening!")

in log file i have warn

[WARN ]  [el.core.internal.ModelRepositoryImpl] - Configuration model 'xxxx.rules' has error, therefore ignoring it : [4,3]: no viable alternative at input 'item'

Where I’m wrong, syntax or something else. Please help

Capital “I” for “Item”

    Item DoorSensor received update OPEN

I’ve been trying for two weeks to get him to work. Thank you very much

Thanks, same for me “Capital I”

This is stupid logic isn´t it

Almost all programming languages, the Rules DSL included, are case sensitive. Languages and computer interfaces where case doesn’t matter are the exception.